(1) Field of the Invention
This invention relates generally to direct current-to direct current (DC-to-DC) converters and relates more specifically to DC-to-DC converters using a novel switching technique.
(2) Description of the Prior Art
Energy saving, i.e. increasing efficiency of electronic systems is getting more and more important. Designers of power systems strive to minimize losses and heat. DC-to-DC converters, which are produced in millions, play an important role in the effort to save energy by improving their efficiency.
Switching DC-to-DC converters can either be designed for continuous switching or in pulse skip mode.
The efficiency reduces for both modes as the switching increases with load.
In continuous mode, the clock is switching continuously and hence the circuit has an associated switching loss.
In pulse skip mode, there is an additional overhead in area and power for the regulator to control the pulse skipping. For pulse skip switching, the clock is continuous till the output achieves a final voltage, and then starts pulse-skipping (skip-mode), where the clock is only available to the circuit when the output voltage falls below a pre-determined level. This clock goes away again once the output is back at the required level. With load applied to the output, the circuit has to switch a lot more to keep the output at the required level.
It is a challenge for the designers of circuits for switching DC-to-DC converters to improve the efficiency of these converters, to reduce the area required of the circuits and to reduce an average input current.
There are known patents or patent publications dealing with switching DC-to-DC converters.
U.S. Pat. No. 7,528,590 to Wei proposes a DC-to-DC boost converter circuit receiving a DC input voltage and converts it to a DC output voltage at a different voltage level than the DC input voltage. The DC to DC boost converter includes a switching power converter for receiving the input voltage on an input and converting the input voltage to an output as the DC output voltage in response to pulse control signals. A switching controller generates the pulse control signals during a switching cycle. The switching controller further includes pulse-skipping circuitry for generating a pulse width modulated signal to the switching power converter.
U.S. Pat. No. 6,469,914 to Hwang et al. discloses a controller for a pulse width modulating (PWM) power converter. The controller monitors an output voltage and a current through a magnetic element for modulating a duty cycle of a main power switch. The controller is an eight-pin integrated circuit that controls either a forward converter or a post regulator without internal modifications. The monitored current of the forward converter forms a positive sensing signal. The monitored current of the post regulator forms a negative sensing signal. A current sense circuit of the controller forms an absolute value of either sensing signal.
U.S. Pat. No. 6,420,858 to Kitagawa et al. describes a DC-to-DC converter circuit having a power saving mode, and which achieves a high conversion efficiency without using a sense resistance. The DC-to-DC converter circuit includes a triangular wave generation circuit to generate a triangular wave signal and a differential amplifier to receive the triangular wave signal and to generate an output signal.
Furthermore there are four more patents dealing with startup circuits for bandgap voltage reference generators:
U.S. Pat. No. 5,751,565 to Faulk describes a switching converter that delivers power to a load at a regulated load voltage based upon switch control pulses from a pulse width modulator (PWM), a circuit monitors directly the level of the load voltage and, when it rises to an upper threshold, the circuit generates a feedback signal for the PWM that interrupts its generation of switch control pulses until the load voltage drops to a lower threshold voltage.
U.S. Pat. No. 5,077,652 to Faley discloses a direct current (DC) to alternating current (AC) converter that receives a direct current signal from an input power source to drive a load. A power module, controlled by a central processing unit, includes a DC-to-DC voltage booster that boosts the direct current signal from approximately 12 volts to 150 volts. A DC-to-AC inverter, which is also controlled by the CPU, converts the boosted DC voltage from DC to a 60 Hz AC output signal used to drive the load. The power module includes a voltage feedback path and a current feedback path for regulating the AC output voltage signal in response to changes in the load.
U.S. Pat. No. 5,499,184 to Squibb discloses a power switch circuit including a small signal transformer and a low power oscillator for detecting the power switch while isolating it from the primary of the power supply. When the power switch is off, or is otherwise pressed to turn off the power supply, the oscillator charges a capacitor. A sensing and control circuit coupled to the oscillator and capacitor grounds a vital signal of the power supply keeping the power supply turned off. In one embodiment, when the switch is turned on, it shorts the signal transformer disabling the oscillator, so that the capacitor is discharged and the sensing and control circuit releases the vital signal.
U.S. Pat. No. 5,498,995 to Szepesi et al. describes Improved controller circuitry for a switching power supply. The switching power supply is of the type having a transformer having primary and secondary windings for generating an output voltage at the secondary winding, a power switch for driving the primary winding, and controller circuitry 100 for activating the power switch. The improved controller circuitry includes an oscillator and frequency shift means. The oscillator generates PWM pulses having a predetermined frequency for use in activating the power switch.